This invention relates to an electronic supply for igniting and operating a high-pressure discharge lamp, comprising first driven main switching means for generating a high-frequency current through inductive means, and switching means suitable for subsequent current supply through the inductive means when the first main switching means are in the non-conducting state, which electronic supply is provided with a transformerless level shifter and with a driver circuit with at least switch drive means for driving the first driven main switching means.
A circuit arrangement of the kind mentioned in the opening paragraph is known from EP-A-0507398. First main switching means and switch drive means in the known supply are constructed as (MOS)FETs to reduce losses during operation. The level shifter is transformerless, which is an important and favorable feature. Although in itself a transformer constitutes an excellent electrical separation device, the use of a transformer, especially in circuits for the supply and operation of high-pressure discharge lamps, has among its disadvantages a comparatively great bulk and a comparatively high heavy weight, also in the case of a low power transfer, and a high degree of unsuitability for integration. The level shifter is further provided with self-induction means for fast switching of the main switching means while switching losses are reduced at the same time. The known supply, which is suitable for generating a high-frequency current with a frequency of approximately 20 kHz, is of practical use up to frequencies of approximately 50 kHz. At frequencies above 50 kHz, however, the inevitable losses are found to assume unacceptable proportions. These losses are formed to a major extent by the dissipation of energy stored in parasitic capacitances of the switch drive means during periodic switching into conduction of the switch drive means.
The use of high frequencies to above 200 kHz, however, is desirable. On the one hand, the use of such high frequencies makes it possible to use small inductive means. On the other hand, the use of high frequencies is favorable for preventing instabilities in lamp operation caused by acoustic resonances. This is of major importance, particularly where high-pressure sodium lamps and metal halide lamps are concerned.